Assessing the Climatic Influence on River in Bangladesh: In Perspective of Morphology and Discharge of Surma River

Bangladesh is a region that is vulnerable to climate change. In this study, the influence of rainfall on river morphology and river discharges was investigated. The morphological analysis of the Surma River was carried out using GIS. Rainfall of Sylhet over 44 years(1972–2016) was analyzed. Annually 434.099 mm rainfall precipitated in Sylhet. The mean annual rainfall from 1972-to 2016 shows a little decreasing trend. 845.99 M3/s of water was discharged on average from the Surma river annually. Over these 44 years, erosion and deposition show a very decreasing rate with a very steep slope. The sinuosity index of the Surma River varies from 1.32 to 2.29. The total erosion is strongly related to annual mean rainfall (r=0.939), which greatly affects the total river erosion. 88% of erosion depends on the annual mean rainfall (r2=0.88). The r between mean annual rainfall and total deposition is 0.919, which presents a very strong positive relationship. More than 80% of the erosion can be explained by rainfall. According to the percentage of r2, about 89.8% of the variables of deposition can be explained by rainfall if other factors remain constant. The river deposition and erosion are very highly dependent on river discharge. The Surma river’s annual mean discharge and rainfall are strongly correlated (r = 0.69), which indicates that the discharge of the Surma river is highly dependent on the surrounding area’s rainfall. To conclude, it can be noted that the Sylhet rainfall decreased from 1972 to 2016, which affected the Surma river’s morphology directly due to climate change.